1. Field of the Invention
The subject invention relates to methods and apparatus for compensating periodic electric signal components in servo control signals and, more specifically, to tachometer type servo systems.
2. Description of the Prior Art
Periodically recurring error signals are a notorious source of malfunction and design and application limitation in servo systems. In particular, a periodic error signal component in a variable input signal of a servo system causes the system to malfunction or at least operate at less than its inherent potential on the one hand and, on the other hand, calls for corrective measures which either render the system expensive or introduce limitations in the full use of the system.
By way of example, periodic error signals in a tachometer signal of a servo of a rotating drive provoke angular velocity perturbations which affect the performance of the system.
The prior-art effort in this area has been mainly concerned with the source of the periodic disturbance. In particular, most remedial attempts have focused on a mechanical perfection of the parts at the location of generation of the periodic disturbance. Pursuant to this attitude the typical remedial approach to periodic error signals in a tachometer signal has culminated in attempts to perfect the tachometer and the equipment coupled thereto and to the associated electromechanical drive.
This, in turn, has introduced design and manufacturing complexities, has increased the expense of the resulting equipment, and has subjugated attainable performance to the dictates of mechanical design and feasibility limitations.
Prior-art attempts to solve the problem electronically have not been sufficiently effective as to permit a material reduction of the need for mechanical solutions of the above mentioned type.